/Engine/Source/Runtime/StaticMeshDescription/Public/StaticMeshOperations.h
Make sure all normals and tangents are valid. If not, recompute them.
static void RecomputeNormalsAndTangentsIfNeeded ( [FMeshDescription](API\Runtime\MeshDescription\FMeshDescription) & MeshDescription, EComputeNTBsFlags ComputeNTBsOptions )